Effects of Cyclic Chronic Heat Stress on the Expression of Nutrient Transporters in the Jejunum of Modern Broilers and Their Ancestor Wild Jungle Fowl

Abstract

Heat stress (HS) has been reported to disrupt nutrient digestion and absorption in broilers. These effects may be more prominent in fast-growing chickens due to their high metabolic activity. However, the underlying molecular mechanisms are not yet fully elucidated. Hence, the current study aimed to evaluate the effect of chronic HS on jejunal nutrient transport in slow- (Athens Canadian Random Bred, ACRB from 1950), moderate- (The 1995 random bred, 95RAN), rapid- (modern broilers, modern random bred, MRB) growing birds and their ancestor wild jungle fowl (JF). One-day male chicks (n = 150/line) were placed by line in environmentally controlled chambers and kept under the same industry-standard environmental conditions until d28. On d29, an 8-h daily cyclic HS (36°C) was applied to half of the chambers, which lasted until d55, while keeping the rest under thermal neutral (TN, 24°C) conditions. Jejunum tissues were collected for morphology assessment and molecular analysis of carbohydrate-, amino acid-, and fatty acid-transporters. MRB exhibited the highest body weight (BW) followed by 95RAN under both conditions. HS decreased feed intake (FI) in MRB and 95RAN, which resulted in lower BW compared to their TN counterparts; however, no effect was observed in ACRB and JF. MRB showed a greater villus height (VH) to crypt depth (CD) ratio under both environmental conditions. Molecular analyses showed that glucose transporter (GLUT) 2, 5, 10, and 11 were upregulated in MRB compared to some of the other populations under TN conditions. HS downregulated GLUT2, 10, 11, and 12 in MRB while it increased the expression of GLUT1, 5, 10, and 11 in JF. GLUT2 protein expression was higher in JF compared to ACRB and MRB under TN conditions. It also showed an increase in ACRB but no effect on 95RAN and MRB under HS conditions. ACRB exhibited greater expression of the EAAT3 gene as compared to the rest of the populations maintained under TN conditions. HS exposure did not alter the gene expression of amino acid transporters in MRB. Gene expression of CD36 and FABP2 was upregulated in HS JF birds. Protein expression of CD36 was downregulated in HS JF while no effect was observed in ACRB, 95RAN, and MRB. Taken together, these data are the first to show the effect of HS on jejunal expression of nutrient transporters in three broiler populations known to represent 70 years of genetic progress in the poultry industry and a Red Jungle Fowl population representative of the primary ancestor of domestic chickens.

Effect of Cyclic Heat Stress on Feeding-Related Hypothalamic Neuropeptides of Three Broiler Populations and Their Ancestor Jungle Fowl

“…As previously shown by our group ( Abdelli et al, 2021 ) and summarized in Table 3 , chronic cyclic HS significantly decreased cumulative FI in both MRB and 95RB, but not in JF and ACRB. The highest cumulative FI was observed in MRB, followed by 95RB, and JF and ACRB regardless of the environmental conditions.…”

“…Intensive genetic selection programs have produced broiler chickens capable of efficiently converting feed into muscle mass ( Clavijo and Flórez, 2018 ) with tremendously high growth rates and processing yields ( Havenstein et al, 1994a , b , 2003a , b ; Zuidhof et al, 2014 ; Tallentire et al, 2016 ). Results reported in our previously published papers ( Orlowski et al, 2020 ; Abdelli et al, 2021 ) are consistent with the improvements in productive performance and slaughter traits ascribable to selection. By outperforming the other lines regardless of the environmental temperature, MRB corroborated the valuable outcomes of selection.…”

“…As recently shown by Abdelli et al (2021) and summarized here ( Table 3 ), the significant drops in FI of 95RB and MRB are a clear reflection of a more pronounced HS susceptibility of hyper-selected broilers than their predecessors. Since FI is tightly controlled by the hypothalamic centers of hunger and satiety ( Simpson et al, 2008 ; Waterson and Horvath, 2015 ; Timper and Brüning, 2017 ; Luquet et al, 2019 ) through a myriad of (an)orexigenic neuropeptides ( Arora and Anubhuti, 2006 ; Furuse et al, 2007 ; Tachibana and Tsutsui, 2016 ; Delgado et al, 2017 ), we sought to determine the expression profile of FRHN in four chicken populations undergoing chronic cyclic HS.…”

“…Body weight (BW) and feed intake (FI) were recorded weekly. The number and BW of dead or culled birds were considered while computing the feed conversion ratio (FCR) of each replicate as previously reported ( Abdelli et al, 2021 ). Sample collection was carried out at the end of the grow-out period (56 days) after feeding all animals and applying, in the appropriate rooms, HS for at least 2 h. Two birds per pen—i.e., 6 birds from each combination of environmental temperature and line—were randomly selected and euthanized by cervical dislocation.…”

Heat Stress Affects Jejunal Immunity of Yellow-Feathered Broilers and Is Potentially Mediated by the Microbiome

“…The jejunum is the middle intestine and is related to most of the nutrients’ digestion and absorption in broilers; accordingly, the jejunum is more susceptible to HS ( Song et al, 2013 ). Furthermore, as a representative segment of the small intestine, the jejunum is always selected for intestinal research, and jejunal immunity plays a crucial role in maintaining gut health ( Song et al, 2014 ; Abdelli et al, 2021 ; Wang C. et al, 2021 ). However, very limited data is available regarding HS exposure’s effects on jejunal immune response in yellow-feathered broilers.…”